1. Field of the Invention
The present invention relates to post-tensioning of concrete. More particularly, the present invention the relates to post-tension anchor systems. More particularly, the present invention the relates to pocketformers that are used for the creation of a pocket in a concrete structure adjacent to the end of the an anchor in an anchor system.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98.
For many years, the design of concrete structures imitated typical steel design of column, girder and beam. With technological advances in structural concrete, however, its own form began to evolve. Concrete has the advantages of lower cost than steel, of not requiring fireproofing, and of its plasticity, a quality that lends itself to free flowing or boldly massive architectural concepts. On the other hand, structural concrete, though quite capable of carrying almost any compressive (vertical) load, is extremely weak in carrying significant tensile loads. It becomes necessary, therefore, to add steel bars, called reinforcements, to concrete, thus allowing the concrete to carry the compressive forces and the steel to carry the tensile (horizontal) forces.
Structures of reinforced concrete may be constructed with load-bearing walls, but this method does not use the full potentialities of the concrete. The skeleton frame, in which the floors and roofs rest directly on exterior and interior reinforced-concrete columns, has proven to be most economic and popular. Reinforced concrete framing is seemingly a quite simple form of construction. First, wood or steel forms are constructed in the sizes, positions, and shapes called for by engineering and design requirements. The steel reinforcing is then placed and held in position by wires at its intersections. Devices known as chairs and spacers are used to keep the reinforcing bars apart and raised off the form work. The size and number of the steel bars depends completely upon the imposed loads and the need to transfer these loads evenly throughout the building and down to the foundation. After the reinforcing is set in place, the concrete, a mixture of water, cement, sand, and stone or aggregate, of proportions calculated to produce the required strength, is placed, care being taken to prevent voids or honeycombs.
One of the simplest designs in concrete frames is the beam-and-slab. This system follows ordinary steel design that uses concrete beams that are cast integrally with the floor slabs. The beam-and-slab system is often used in apartment buildings and other structures where the beams are not visually objectionable and can be hidden. The reinforcement is simple and the forms for casting can be utilized over and over for the same shape. The system, therefore, produces an economically viable structure. With the development of flat-slab construction, exposed beams can be eliminated. In this system, reinforcing bars are projected at right angles and in two directions from every column supporting flat slabs spanning twelve or fifteen feet in both directions.
Reinforced concrete reaches its highest potentialities when it is used in pre-stressed or post-tensioned members. Spans as great as 100 feet can be attained in members as deep as three feet for roof loads. The basic principal is simple. In pre-stressing, reinforcing rods of high tensile strength wires are stretched to a certain determined limit and then high-strength concrete is placed around them. When the concrete has set, it holds the steel in a tight grip, preventing slippage or sagging. Post-tensioning follows the same principal, but the reinforcing is held loosely in place while the concrete is placed around it. The reinforcing is then stretched by hydraulic jacks and securely anchored into place. Pre-stressing is done with individual members in the shop and post-tensioning as part of the structure on the site.
In a typical tendon tensioning anchor assembly in such post-tensioning operations, there is provided a pair of anchors for anchoring the ends of the tendons suspended therebetween. In the course of installing the tendon tensioning anchor assembly in a concrete structure, a hydraulic jack or the like is releasably attached to one of the exposed ends of the tendon for applying a predetermined amount of tension to the tendon. When the desired amount of tension is applied to the tendon, wedges, threaded nuts, or the like, are used to capture the tendon and, as the jack is removed from the tendon, to prevent its relaxation and hold it in its stressed condition.
In such post-tension construction, the tendons are anchored and cut off just inside the face of the structure in what are termed “pockets.” The “pockets” are simply voids in the concrete structure that provide access to the end of the anchor that is cemented within the concrete structure and to the tendon that extends through the anchor and out of the concrete structure. The pocket allows a device, such as a plasma cutter, to be used to cut the tendon near the end of the anchor body. U.S. Pat. No. 5,436,425, issued on Jul. 25, 1995 to the present inventor, discloses a method and apparatus for a plasma cutter that can be used to cut a tendon within a pocket. Once the end of the tendon is cut near the end of the anchor, the pocket is filled with a concrete grout so as to conceal the end of the anchor and the tendon from the elements and give the concrete structure a smooth outer surface.
Pockets are formed by using a pocketformer. A pocketformer is typically a plastic structure that is mounted to the end of an anchor before concrete is poured over the anchor and tendon. After concrete is poured and suitably hardened, a form board is removed and the pocketformer is removed from the end of the anchor so as to expose the pocket. Typical pocketformers as used in the prior art have a frustoconical surface on the exterior of the pocketformer. The frustoconical shape defines the pocket. A central tubular member is formed within the interior of the frustoconical portion. One end of the tubular member extends into the central bore of the anchor. The interior of the tubular member allows the tendon to extend therethrough. The tubular member is generally centered within the interior of the frustoconical portion. The surface of the anchor will abut the narrow end of the frustoconical portion. The wide end of the frustoconical portion will abut a surface of a form board. The tubular member extends through a hole in the form board. As such, the tendon will extend outwardly of the form board during the formation of the concrete structure.
One of the problems associated with the prior art pocketformers is the inability to accommodate tendon cutting devices so that the tendon can be cut near the end of the anchor within the pocket. In particular, prior art pocketformers have a problem accommodating a plasma torch for cutting the tendon near the end of the anchor.
Various patents have issued relating to pocketformers shaped so as to receive tendon cutting devices therein. For example, U.S. Pat. No. 3,844,697, issued on Oct. 28, 1974 to Edwards, discloses an anchorage assembly including an anchor having a hollow housing and means therein for engaging a stressing tendon passing therethrough. The assembly includes a hollow member removably attached to the anchor housing and to the concrete formwork. The hollow member fixes the relative position of the anchor housing to the formwork. The hollow member surrounds the tendon between the anchor housing and the formwork and is adapted and arranged to be detached from the anchor housing after the concrete has set. A cavity-forming spacer is provided which surrounds the member and is disposed between and seals against the anchor housing in the formwork to form a cavity in the concrete. The spacer is adapted and arranged to be removed from around the hollow member after the concrete has set.
U.S. Pat. No. 5,897,102, issued on Apr. 27, 1999 to the present inventor, describes a pocketformer apparatus for a post-tension anchor system. This pocketformer apparatus includes a tubular member with an outwardly flanged end, a securement member affixed to the tubular member, and a cup member having an interior opening such that the tubular member extends through the interior opening. The tubular member has an interior passageway extending from the flanged end to another end. The flanged end engages an anchor of the post-tension anchor system. The cup member is interposed between the flanged end and the securement member on the tubular member. The tubular member has an externally threaded area extending inwardly of the end opposite the flanged end. The securement member is threadedly received by the externally threaded area. An annular ring is formed on the flanged end of the tubular member so as to engage a receptacle formed in the encapsulation of the anchor. The securement member, the cup member and the tubular member are formed of a polymeric material.
U.S. Pat. No. 6,393,781, issued on May 28, 2002 to the present inventor, describes a pocketformer apparatus for post-tension construction. The pocketformer apparatus has an anchor member having a wedge-receiving cavity therein, a tubular member having a portion extending through the wedge-receiving cavity, a first securement member affixed to a first end of the tubular member, a cup member positioned over the tubular member, and a second securement member affixed to a second end of the tubular member. The cup member is interposed between the second securement member and the anchor member. The tubular member also extends through a hole in a form board. The second securement member is positioned on one side of the form board. The cup member and the anchor member are positioned on an opposite side of the form board. A tendon extends through the tubular member.
U.S. Pat. No. 7,174,685, issued on Feb. 13, 2007 to Hayes, discloses an apparatus and method for reducing corrosion in post-tensioning construction. An anchor is engageable with a post-tension tendon and comprises an anchor base and a sheath engaged with the anchor base, and a cap for sealing a portion of the tend within the anchor. The sheath can include an extension having a contact end distal from the anchor base for contacting the tendon as the tendon is inserted through the extension and the anchor base aperture. The cap can extend completely through the anchor base for connection of the anchor base of a sheath or sheath extension attached to the base. A pocketformer is attachable to the sheath for generating a void in the concrete.
One of the problems associated with these prior art pocketformer patents is that the pockets formed by the pocketformers tend to accumulate metal and heat generated by the use of a plasma cutter to cut the tendon in the pocket. Thus, there is need for a pocketformer that can form a pocket that channels the heat and metal particulate matter generated by a plasma cutter away from the anchorage system.
It is an object of the present invention to provide a pocketformer for an anchorage system.
It is another object of the present invention to provide to a pocketformer that easily fits over an end of an anchor body.
It is another object of the present invention to provide a pocketformer that forms a pocket that can channel heat generated by a plasma cutter away from the anchorage system.
It is still another object of the present invention to provide a pocketformer that creates a pocket that channels metal particulates away from anchorage system.
It is another object of the present invention to provide a pocketformer that creates a pocket that easily accommodates tendon-cutting devices.
It is another object of the present invention to provide a pocketformer that creates a pocket for accommodating a plasma cutter.
It is another object of the present invention to provide a pocketformer that is easily removed from hardened concrete.
It is another object of the present invention to provide a pocketformer that is lightweight and inexpensive.
These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims.